[time-nuts] NTBW50AA Power supply

Bob Camp lists at rtty.us
Tue Sep 3 10:53:24 EDT 2013


Hi

The application for all these boxes is cell tower infrastructure. Some of the world likes the old style 48 volt power (like the old AT&T) and some like 24 volt power.  The spec sheet is written so that either the 24 volt guys or the 48 volt guys will be happy with the part. I don't know of anybody who wants to put 35 volts into a chunk of cell tower gear. 

The way switchers are designed (it's just a standard brick supply) they are quite happy over a voltage range with no ranging or fiddling. I would not try to operate one at the very bottom or top end of it's spec, but anything in the middle should keep them quite happy. You don't want to have the supply trip out (under or over) when you have a power burp. 

Your bulk supply should do just fine. The only gotcha would be if it's got a habit of passing line transients. A fast transient might get past a giant electrolytic / not be damped by the transformer inductance. It's not something I'd worry about.. 

I have several of the Nortel / Trimble units running with no problems on any of them. One's on a bulk 24 v supply, one is on a dual lab supply set to +/- 15V and the other is on a 48 volt bulk supply. 

Bob

On Sep 3, 2013, at 9:46 AM, quartz55 <quartz55 at hughes.net> wrote:

> Well, reading the spec sheet, it says -48VDC (-40Vdc min, -60Vdc max) at 2.8A for warm up and .6 during run time <350mv ripple, OR +24Vdc (20Vdc min, 30Vdc max) at 3.57A for warm up and 1.03A run <240mv p-p ripple.  I'm assuming that after the bridge there's some sort of switcher that feeds the unit +5,+12, -12, which I understand is typical for the Thunderbolt units.  But I don't have this thing in hand yet.  It very well may work off +-12V which is essentially 24V, but I doubt if it will work if the voltage is too low, but I'm just speculating.  I know it won't work of 0V which is between 12 and -48.  It may be a variation on one of those 90-220VAC input switchers that's made to work off DC.  It may just be the way they had to write the specs, but will work with about anything.
> 
> I'm not trying to be picky here, I don't want to mess up right off the bat.  Looks like I may be able to use this 5A transformer that puts 35V out of a bridge circuit into an 8200uF cap, but I need to measure the ripple at 1A or so.  I can always add a lot more uF.
> 
> Thanks for those links to the supplies though.
> 
> Yeah, I see where the digital ground is used for the supply return, not the case so the PS should be isolated pretty well.
> 
> Is anyone using one of these particular units?
> 
> Dave
> N3DT
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